The laser shoots 90 kilometers into the atmosphere, where it interacts with the 10-kilometer-thick layer of sodium atoms left around our planet by meteoroid impacts. The laser makes the sodium fluoresce, producing a bright point of light

The only news here is that they’re using a new laser “more flexible and reliable than the previous one”. The technique itself is kinda old news, but here’s how it works : They measure the atmospheric distorsion and compensate for it by deforming the surface of the telescope’s mirror in real time. It’s called adaptive optics.http://en.wikipedia.org/wiki/Adaptive_optics

The bright point of light wavers due to atmospheric distortion. This distortion can be accounted for by moving parts of the telescope mirror in real time. This way much of the atmospheric distortion is eliminated.